U.S. Pat. No. 4,283,229 (Girg et al.) discloses that stable suspensions of nonionic cellulose ethers can be prepared in a solution of 4 to 12% electrolyte if alumina is added to the suspension. Prior art aqueous fluid suspensions of water soluble polymers are further described in U.S. Pat. Nos. 4,883,536 and 4,883,537. U.S. Pat. No. 4,883,536 covers the use of ammonium salts such as diammonium sulfate (DAS), diammonium phosphate (DAP) and ammonium polyphosphate for preparing fluid suspensions of water soluble polymers. U.S. Pat. No. 4,883,537 covers the use of concentrated aqueous potassium carbonate for preparing suspensions of sodium carboxymethylcellulose.
The art of U.S. Pat. No. 4,883,536 is limited in that the compositions described all contain ammonium ion. This chemical species is disadvantageous due to the possible release of small amount of ammonia when incorporated into a number of end use applications such as joint compound or paint. In contrast to this, the present invention does not contain ammonium ion and thus can not generate undesirable fumes in end use applications.
The art of U.S. Pat. No. 4,883,537 describes suspensions of water soluble polymers in concentrated aqueous potassium carbonate media. The drawback to this latter prior art technology is that suspensions prepared according to this art exhibit very high pH (greater than 12.5). The high pH of this prior art is severely limiting since the use of such a thickening agent can cause adverse reactions. In addition, the high pH of this prior art thickener makes it a hazardous material requiring extreme caution in handling. In contrast to this, the present invention exhibits a moderate pH of about 9.0 that is acceptable for use in a number of applications where the prior art may be precluded from use.